1. Field of the Invention
This invention relates to crystalline molecular sieves which encapsulate macrocyclic organic molecules that can complex metals, method for preparation of the molecular sieves and uses thereof.
2. Description of the Prior Art
Zeolite materials, both natural and synthetic, have been demonstrated in the past to have catalytic properties for various types of hydrocarbon conversion. Certain zeolitic materials are ordered, porous, crystalline aluminosilicates having a definite crystalline structure as determined by X-ray diffraction, within which there are a large number of smaller cavities and channels or pores. These cavities and pores are uniform in size within a specific zeolitic material. Since the dimensions of these pores are such as to accept for adsorption molecules of certain dimensions while rejecting those of larger dimensions, these materials have come to be known as "molecular sieves" and are utilized in a variety of ways to take advantage of these properties.
Zeolites typically have uniform pore diameters of about 3 Angstroms to about 10 Angstroms. The chemical composition of zeolites can vary widely and they typically consist of SiO.sub.2 in which some of the silicon atoms may be replaced by tetravalent ions such as Ti or Ge, by trivalent ions such as Al, B, Ga, Fe, or by bivalent ions such as Be, or by a combination of any of the aforementioned ions. When there is substitution by bivalent or trivalent ions, cations such as Na, K, Ca, NH.sub.4 or H are also present.
Representative samples of siliceous zeolites are small pore zeolites such as NaA, CaA, Erionite; medium pore zeolites such as ZSM-5, ZSM-11, ZSM-22, ZSM-23, ZSM-48, ZSM-12, zeolite beta; and large pore zeolites such as zeolite L, ZSM-4 (omega), NaX, NaY, CaY, REY, US-Y, ZSM-20, and mordenite.
Zeolites include a wide variety of positive ion-containing crystalline aluminosilicates. These aluminosilicates can be described as a rigid three-dimensional framework of SiO.sub.4 and AlO.sub.4 in which the tetrahedra are cross-linked by the sharing of oxygen atoms whereby the ratio of the total aluminum and silicon atoms to oxygen atoms is 1:2. The electrovalence of the tetrahedra containing aluminum is balanced by the inclusion in the crystal of the cation, for example an alkali metal or an alkaline earth metal cation. This can be expressed wherein the ratio of aluminum to the number of various cations, such as Ca/2, Sr/2, Na, K or Li, is equal to unity. One type of cation may be exchanged either entirely or partially with another type of cation utilizing ion exchange techniques in a conventional manner. By means of such cation exchange, it has been possible to vary the properties of a given aluminosilicate by suitable selection of the cation. The spaces between the tetrahedra are occupied by molecules of water prior to dehydration.
Prior art techniques have resulted in the formation of a great variety of synthetic zeolites. The zeolites have come to be designated by letter or other convenient symbols, as illustrated by Zeolite A (U.S. Pat. No. 2,882,243), Zeolite X (U.S. Pat. No. 2,882,244), Zeolite Y (U.S. Pat. No. 3,130,007), Zeolite Beta (U.S. Pat. No. 3,308,069), ZK-5 (U.S. Pat. No. 3,247,195), ZK-4 (U.S. Pat. No. 3,314,752), ZSM-5 (U.S. Pat. No. 3,702,886), ZSM-5/ZSM11 intermediate (U.S. Pat. No. 4,229,424), ZSM-23 (U.S. Pat. No. 4,076,842), ZSM-11 (U.S. Pat. No. 3,709,979), ZSM-12 (U.S. Pat. No. 3,832,449), ZSM-20 (U.S. Pat. No. 3,972,983), ZSM-35 (U.S. Pat. No. 4,016,245), ZSM-38 (U.S. Pat. No. 4,046,859), and ZSM-48 (U.S. Pat. No. 4,375,573), merely to name a few. All of the above patents are incorporated herein by reference.
The silicon/aluminum atomic ratio of a given zeolite is often variable. For example, Zeolite X can be synthesized with silicon/aluminum atomic ratios of from 1 to 1.5; zeolite Y, from 1.5 to about 3. In some zeolites, the upper limit of the silicon/aluminum atomic ratio is unbounded. ZSM-5 is one such example wherein the silicon/aluminum atomic ratio is at least 12. U.S. Pat. No. 3,941,871 (U.S. Pat. No. Re. 29,948) discloses a porous crystalline silicate made from a reaction mixture containing no deliberately added aluminum in the recipe and exhibiting the X-ray diffraction pattern characteristic of ZSM-5 type zeolites. U.S. Pat. Nos. 4,061,724, 4,073,865 and 4,104,294 describe crystalline silicas of varying aluminum and metal content. These zeolites can consist essentially of silica, containing only traces or no detectable amounts of aluminum.
Another class of molecular sieves consists of AlO.sub.2.PO.sub.2 units (AlPO.sub.4) whose Al or P constituents optionally may be substituted by other elements such as Si (called silicoaluminophosphates or SAPO's), or metals (called metaloaluminophosphates or MeAPO's) or combinations thereof (called metaloaluminophosphosilicates or MeAPSO's). As with aluminosilicates, the ALPO.sub.4 's, SAPO's, MeAPO's and MeAPSO's are crystalline and have ordered pore structures which accept certain molecules while rejecting others and they are often considered to be zeolitic materials.
Aluminum phosphates are taught, for example, in U.S. Pat. Nos. 4,310,440 and 4,385,994. These aluminum phosphate materials have essentially electroneutral lattices. U.S. Pat. No. 3,801,704 teaches an aluminum phosphate treated in a certain way to impart acidity. Other patents teaching aluminum phosphates include U.S. Pat. Nos. 4,365,095; 4,361,705; 4,222,896; 4,210,560; 4,179,358; 4,158,621; 4,071,471; 4,014,945; 3,904,550; and 3,697,550.
Silicoaluminophosphates of various structures are taught in U.S. Pat. No. 4,440,871. Aluminosilicates containing phosphorous, i.e. silicoaluminophosphates of particular structures are taught in U.S. Pat. Nos. 3,355,246 (i.e. ZK-21) and 3,791,964 (i.e. ZK-22). Other teachings of silicoaluminophosphates and their synthesis include U.S. Pat. Nos. 4,673,559 (two-phase synthesis method); 4,623,527 (MCM-10); 4,639,358 (MCM-1); 4,647,442 (MCM-2); 4,664,897 (MCM-4); 4,638,357 (MCM-5); and 4,632,811 (MCM-3).
Compositions comprising crystals having a framework topology after heating at 110.degree. C. or higher giving an X-ray diffraction pattern indicating pore windows formed by 18 tetrahedral members of about 12-13 Angstroms in diameter are taught in U.S. Pat. No. 4,880,611.
A method for synthesizing crystalline metaloaluminophosphates (MeAPO's) is shown in U.S. Pat. No. 4,713,227, and an antimonophosphoaluminate and the method for its synthesis are taught in U.S. Pat. No. 4,619,818. U.S. Pat. No. 4,567,029 teaches metalloaluminophosphates, and titaniumaluminophosphate and the method for its synthesis are taught in U.S. Pat. No. 4,500,651.
All of the above patents are incorporated herein by reference.
The precise crystalline microstructure of crystalline molecular sieves manifests itself in a well-defined X-ray diffraction pattern that usually contains many sharp maxima and that serves to uniquely define the material. Similarly, the dimensions of the pore and the internal cage structures are very regular, due to the precise repetition of the crystalline microstructure.
Prior techniques for synthesizing crystalline molecular sieves have involved the preparation of solutions containing oxide sources and organic molecules. It has been theorized that the organic molecules may act as templating agents around which the molecular sieve crystallizes. However, in general, there is no clear correlation between specific organics and crystalline structure of the molecular sieve. Therefore, although a resulting crystalline structure which has been synthesized in the presence of an organic molecule may be observed and its X-ray diffraction pattern determined, it is often not clear what exact role the organics play in the synthesis.
Metals have been introduced into molecular sieves by ion exchange, impregnation, codeposition, adsorption from a gaseous phase, introduction of metal compounds during crystallization or absorption of metal vapor to introduce a metal component into pore cavities or onto the surfaces.
There has been no suggestion to introduce metal into a molecular sieve as part of a bicyclic organic complex or ligand which is highly stable and can retain its integrity during and after crystallization.
Accordingly, it is an object of the invention to provide microporous, tetrahedral framework crystalline molecular sieves containing immobilized ion specific bicyclic chelating agents.